1. Field of the Invention
The present invention relates to a glass composition and an optical member and an optical instrument using the glass composition.
2. Related Background Art
The demand for materials having a high refractive index has been increasing year after year in the field of optical instruments and the like. For example, a glass having a refractive index nd of nearly 2.0 for a light (d line) having a wavelength of 587.562 nm is becoming more commonly used in optical instruments, such as digital cameras. As such materials having a high refractive index, a glass composition containing tellurium oxide (TeO2) and lead oxide (PbO) for improvement of the refractive index have been disclosed, for example.
For example, Japanese Unexamined Patent Application Publication No. Sho 62-128946 discloses a glass composition having the following composition in mol %: 10 to 85% TeO2; 1 to 50% PO5; 1 to 50% PbO; 0 to 30% Li2O; 0 to 40% ZnO; a total amount of Li2O and ZnO in a range from 1 to 40%; 0 to 30% Na2O; 0 to 30% K2O; 0 to 25% Rb2O; 0 to 20% Cs2O; a total amount of Na2O, K2O, Rb2O, and Cs2O in a range from 0 to 30%; 0 to 20% MgO; 0 to 20% CaO; 0 to 20% SrO; 0 to 35% BaO; a total amount of MgO, CaO, SrO, and BaO in a range from 0 to 35%; 0 to 5% Ta2O5; 0 to 20% Nb2O5; a total amount of Ta2O5 and Nb2O5 in a range from 0 to 20%; 0 to 15% SiO2; 0 to 25% GeO2; 0 to 30% B2O3; 0 to 10% Al2O3; 0 to 20% Sb2O3; 0 to 15% In2O3; 0 to 4% La2O3; 0 to 4% Y2O3; 0 to 4% Gd2O3; 0 to 4% Yb2O3; 0 to 4% ZrO2; 0 to 10% Bi2O3; 0 to 20% TiO2; and 0 to 7% WO3.
Meanwhile, Japanese Examined Patent Application Publication No. Hei 5-73702 discloses a glass composition having the following composition in weight %: 5 to 80% TeO2; 1 to 70% PbO; 1 to 40% B2O3; 1 to 60% Bi2O3; 1 to 20% Al2O3; 0 to 50% ZnO; 0 to 30% WO3; 0 to 20% MgO; 0 to 20% CaO; 0 to 30% SrO; and 0 to 30% BaO.